1. Field of the Invention
The present invention relates to a hydraulic torque transmitting device, such as a fluid coupling or a torque converter, for use in an automatic transmission for an automobile, etc. and particularly of the type provided with a lock-up clutch.
2. Description of the Prior Art
A prior art lock-up torque converter has a pump impeller integrally connected to an input shell, a turbine runner disposed in toroidal fluid flow relation to the pump impeller and splined or otherwise attached to an output shaft for rotation therewith, and a lock-up clutch for providing a direct mechanical drive between the input shell and the output shaft.
With the prior art structure, the pump impeller and turbine runner, which have a relatively large inertia, are essentially driven to rotate together with the input shell and the output shaft during engagement of the lock-up clutch. Due to this, in the case of engagement of the lock-up clutch, a booming sound or like noise is caused by the rotation of the pump impeller and turbine runner, resulting in noisy operation of the torque converter. Further, rotation of the pump impeller inevitably causes the working oil within the converter to be stirred, resulting in a loss of energy and, therefore, a deteriorated power transmitting efficiency.